Fabrication of microchannels in lithium tantalate by selective etching of structures inscribed with a femtosecond laser

Abstract

Selective etching of material areas modified by femtosecond laser pulses in the volume of lithium tantalate has been applied to produce hollow microchannels. In a fully monolithic approach, microchannels up to 2.5 mm long with cross sections of 2.5 µm × 20 µm were etched into the crystal volume at a depth of 430 µm. The influence of the laser repetition rate, the pulse energy and the writing speed on the etching time and the etching selectivity was investigated as part of a systematic study. Characteristic process parameters, i.e. selectivity and diffusion coefficient were determined by fitting the etch depth versus time using a superdiffusion model. The obtained parameters are suitable for predicting the results of selective etching for certain process parameters, and thus enable the process to be controlled. A similar study was carried out in sapphire for comparison purposes.